Sudden and Random LP Gain Halt.

Has anybody experienced this? I made it to Platinum for the first time this year, currently P4 17 lp. I was climbing smoothly, gaining 18 to 20 lp per win and losing an equal amount. Went on a 4 loss streak upon hitting p4 but was luckily not demoted. Came back after a few days and dodged two games... was at -6lp. Then won 3. Gained 18. Then 19. Then ONLY 9 out of the blue. I've never seen this happen before and it kind of has me freaked out a bit. Any ideas??